The present invention relates to a process for producing a semiconductor device, and more particularly, to a process for producing a semiconductor device characterized by effectively removing etching products retained in a treating room.
With recent higher integration of semiconductor devices, circuit patterns become finer and finer to make required processing dimensional accuracy severer. Under such circumstances, reproducibility of treated state becomes important.
For example, in an etching process wherein high processing accuracy is required, in order to realize an anisotropic etching, there is realized a process wherein etching is conducted while protecting side walls with a polymer produced by the etching. But the production of polymer changes depending on the amount of etching product retained in a treating room and wafer temperature. Thus, when the amount of reaction products retained in the treating room changes in each treatment, deposition state of side wall protective film causes deviation among wafers, resulting in causing a problem of poor reproducibility of etching shape. In a recent production process of semi-conductors, even if a deviation of processing dimension is about 10 nm or less, there sometimes produce defective devices.
Further, an etching product retaining in the treating room forms a deposited film on inner wall of the etching apparatus, and peels off when the film thickness reaches to some extent to attach to wafer surface. Such peeled materials are called as contaminants and function as masks at the time of etching processing to produce etching residues, which are one important cause for defective products.
In order to remove such etching products, for example, JP-A-5-144779 proposes to improve quality of the deposited film formed on inner wall of the etching apparatus, and JP-A-7-153751 proposes to conduct dry cleaning using plasma of mixed gases of oxygen gas and chlorine gas.
According to JP-A-5-144779, etching is conducted under conditions for improving the quality of film so as to make the deposited film on inner wall of etching apparatus hardly peeled off. According to this reference, prevention of generation of contaminants may be effective due to difficult peeling of the deposited film on the inner wall of the apparatus, but it is impossible to solve the problem of shift of etching ability by the deposited substance due to a premise of retaining the deposited substance.
According to JP-A-7-153751, a step for plasma cleaning is provided during etching treatment separated from an etching step, said process being characterized by a material to be etched and an etching gas, or a photo-resist made from a carbon compound which is a mask material at the time of etching and a gas composition for removing so-called etching products generated by polymerization of etching gas. According to this process, by removing etching products at each interval of treatment so as to make the reaction products retained in the treating chamber not exceed a predetermined amount, the reproducibility of etching shape is retained within a predetermined value and the formation of deposited film on inner wall of etching apparatus is to be prevented. But the step for plasma cleaning conducted separately from the etching step during etching treatment is a step not pertaining to the production, and thus equal to xe2x80x9cdowntimexe2x80x9d (a time when the apparatus is stopped) from the viewpoint of productivity. Therefore, this process considers cleaning effect for the etching products, but does not consider productivity.
It is an object of the present invention to provide a process for producing a semiconductor device overcoming the problems of prior art mentioned above, said process capable of attaining reproducibility of treatment state and lowering of contaminants by removing reaction products retained in a treating room, while assuring productivity.
The present invention provides a process for producing a semiconductor device using a plasma treating apparatus comprising an etching treatment room, a substrate stage for placing a semiconductor substrate thereon installed in the etching treatment room, a plasma generating means for generating plasma in the etching treatment room, and a gas introducing means for introducing a treating gas into the etching treatment room,
said process comprising subjecting the semiconductor substrate placed on the substrate stage to etching treatment using gases,
wherein the etching treatment comprises at least two steps using different gas compositions in each step in the same etching treatment room continuously, and at least one step comprises using a gas capable of decomposing and vaporizing compounds produced by the etching treatment.
The present invention also provides a process for producing a semiconductor device mentioned above, wherein the substrate stage has an electrode for electrostatic adsorption and the decomposing and removing step is used for further removing electrode voltage and charge stored in the semiconductor substrate.
The present invention further provides a plasma etching treatment apparatus used for the above-mentioned processes, and a semiconductor device thus produced.